For example, Patent Citation 1 discloses the following technique: In one in which a power output of an internal combustion engine is restricted when an accelerator pedal and a brake pedal are depressed at the same time, the power output restriction of the internal combustion engine is removed even in a condition where the brake pedal is being depressed, if an amount of change of the accelerator pedal in a direction of depression is not smaller than a certain amount.
In this Patent Citation 1, the power output restriction is removed if an accelerator operation degree is not smaller than the certain amount. Accordingly, in case that a brake operation signal is not immediately restored (for example, a brake switch is not immediately turned OFF) owing to the viscosity of brake oil when an outside temperature is low even if the accelerator pedal is not stuck in the condition of being depressed, the fact that no acceleration is accomplished upon continuation of the power output restriction of the internal combustion engine can be prevented.
Additionally, since the power output restriction is removed if the amount of change of the accelerator operation degree is not smaller than the certain amount, the fact that running becomes difficult upon continuation of the power output restriction can be prevented even in case that a trouble arises in a condition where a brake operation signal is at ON-state, i.e., even in case of a trouble in which a signal representing continuation of brake operation is being outputted regardless of depression or non-depression of the brake pedal.
However, in such Patent Citation 1, if the amount of change of the accelerator operation degree is not smaller than the certain amount, the power output restriction of the internal combustion engine is removed even though a driver does not intend to do it. Accordingly, even in case that the power output restriction is necessary upon the fact that the accelerator pedal is caught by a floor mat or the like and therefore cannot be restored from its depressed state, there is a problem that the power output restriction is unavoidably removed if the amount of change of the accelerator operation degree becomes not smaller than the certain amount under vehicle vibration or the like.